Scott Marlowe pisze:
So still I don't get this: select * from table; on old server takes 0,5 sec,
on new one takes 6sec. Why there is so big difference? And it does not
matter how good or bad select is to measure performance, because I don't
measure the performance, I measure the relative difference. Somwhere there
is a bottleneck.
Yep, the network I'd say. How fast are things like scp between the
various machines?
Sure it is, but not in a way one could expect:
- scp from 1000Gbit laptop to old server 27MB/sec
- scp from the same laptop to new server 70MB/sec
Both servers have 1000Gbit connection. So it is still mysterious why old
server makes 9x faster select?
I don't claim that something is slow on new (or even older) server. Not
at all. the application works fine (still on older machine). I only
wonder about those differences.
4. Machine. The new server has 5 SAS disks (+ 1 spare), but I don't remember
how they are set up now (looks like mirror for system '/' and RAID5 for rest
- including DB). size of the DB is 405MB
Get off of RAID-5 if possible. A 3 Disk RAID-5 is the slowest
possible combination for RAID-5 and RAID-5 is generally the poorest
choice for a db server.
Sure I know that RAID-5 is slower than mirror but anyway how much
slower? And for sure not as much as single ATA disk.
I refer you to this classic post on the subject:
http://www.mail-archive.com/pgsql-general@xxxxxxxxxxxxxx/msg93043.html
Well, this thread is about benchmarking databases (or even worse,
comparison between two RDBMS). I'm not benchmarking anything, just
compare one factor.
P.
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